Silicone Injection Moulding
Multi-Station Molds: Rotational Molds
In 2-Shot injection molding, a polymer is injected over a molded plastic insert to combine the best features of different materials while reducing or eliminating additional assembly operations. This reduction or elimination of post-processing steps is one of the biggest economical advantages of the 2-Shot silicone injection moulding process. For this kind of silicone injection moulding, a multi-shot mold is needed. There are several types of multi-shot silicone injection moulding available, such as over-molds, core-back, and multi-station molds. The right mold selection depends on part geometry, volume, quality, and molder capacity/capability.
One method of multi-component silicone injection moulding employs a rotating mold and multiple injection units. Once the insert is molded, a hydraulic or electric servo drive rotates the core and the part by 180 degrees (or 120 degrees for a three-shot part), allowing alternating polymers to be injected.
Fig. 1: Multi-Station Rotational Mold
When compared to other methods, such as insert overmolding, this is the fastest and most common method because two or more parts can be molded in every cycle. However, this also presents a challenge, as the manufacturer has to fine-tune the process precisely in order to reach the perfect degree of cure in the LSR and still have a short cooling time in the thermoplastic component. Another advantage of the silicone injection moulding process is the possibility of more complex part geometries than that with the core-back technology, while the general design of the mold remains simpler.
As the 2-Shot silicone injection moulding allows the insertion of the LSR exactly where its function is needed, the production is very cost-effective. Following the trend of this emerging technology and assuring its position as leader in the 2-Shot LSR injection molding industry, SIMTEC Silicone Parts added two additional 250 ton machines in the first half of 2011.
Another multi-station silicone injection moulding is a transfer mold. Find out more about transfer mold presses!
Additional information can be found in our “Tech Info” section.
 Schmachtenberg, E., and Johannaber, F.,2007, “Verfahrensprinzipien und Definition,” Technical Conference Montagespritzgießen, Institute of Polymer Technology, Erlangen, Germany, p. 1-18.
 Schmachtenberg, E., Schuck, M., and Kuehnert, I.(2007), “Forming and Assembly in One Process” Kunststoffe International, p. 8-13.
 Kazmer, D.O.,2007, Injection Mold Design Engineering, Hanser Publishers, Munich.
At SIMTEC Silicone Parts, a leading company in manufacturing high precision parts and components, we are exclusively focused and specialized in the production of LSR and 2-Shot (LSR/Thermoplastic) components.
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